The invention relates to a backflow preventer, which can be integrated into a gas or liquid line and which is provided with a closing body, embodied as a hollow body open at the drainage side. The closing body limits a passage channel between itself and a central closing body counterpart, with the closing body being displaceable by the flow medium flowing through the passage channel from a closing position, contacting the closing body counterpart in a sealing manner, into an opening position against the restoring force of its own elasticity and/or own stability.
Such backflow preventers are inserted into sanitary water lines, for example, in order to prevent the backflow of water and in particular the return suction of waste water into the drinking water lines. Such backflow preventers open when the water flows to an outlet. Here, the closing body is displaced by the flow medium, flowing in the flow direction or in the direction towards the outlet, from its closed position into the open position against the restoring force of a return spring. In the event of an undesired backflow, however, the closing body is pressed firmly against the valve seat and kept in its closing position, thus blocking the way back for the return flowing water.
The backflow preventers of prior art are usually comparatively complicated and comprise multiple components, thus they are expensive in their production. Therefore, the object of the invention is to provide a backflow preventer characterized in a simple construction, with this simple construction favoring low production costs and operation without malfunction.
From CH 572 179 A1 a backflow preventer of the type mentioned at the outset is known, which can be inserted into a gas or liquid line. The known backflow preventer is provided with a cone-shaped closing body on its drainage side which is made from an elastic material, limiting a passage channel between itself and a central closing body counterpart. In a closing position the closing body contacts the closing body counterpart in a sealing manner, which has a cone-shaped exterior contour and is provided circumference penetrations at its exterior for the fluid flowing through the closing body counterpart. The closing body, which contacts the closing body counterpart and thus closes the penetrations in a tightly sealing manner, is displaced by the fluid flowing through the passage channel in the flow direction against the restoring force of its own elasticity in the opening position. In contrast thereto, the fluid flowing opposite the flow direction is able to additionally press the closing body against the exterior circumference of the closing body counterpart.
The use of such backflow valves in the field of one-lever mixing faucets is frequently plagued with the problem that during the closing of the cold water or warm water side, the water, which is enclosed between the closed backflow valve, on the one hand, and the also closed valve seat, on the other hand, is heated to a large extent by exterior influences, until system pressure develops which leads to damages in the weakest part of the supply line and, thus, frequently at the backflow valve. Ultimately, this can lead to a blockage of the supply line or an also undesired cross-flow.
Due to the fact that the closing body provided in CH 572 179 A5 is pressed more and more tightly against the exterior circumference of the closing body counterpart by the pressure of the fluid flowing back against the flow direction, undesired high pressure can develop in the backflow preventer known from CH 572 179 A5.
Two backflow preventers having a construction to that described in CH 572 179 A5 are known from DE 1 154 982 B and DE 842 567 C, with their use also being subject to the disadvantages and risks described above.